Extensible antenna



March14,19 4. o. E. WAGENKNECHT 2,343 9 EXTENS I BLE ANTENNA Filed March 17. 1941 2 Sheets-Sheet 1 March 1944- o. E. WAGENKNECHT 2,3

EXTENSIBLE ANTENNA Filed March 17, 1941 2 Sheets-Sheet 2 Patented Mar. 14, 1944 EXTENSIBLE ANTENNA Otto E. Wagcnknecht, Chicago, 111. assignor to Zenith Radio Corporation, Chicago, 111., a corporation of Illinois Application March 17, 1941, Serial No. 383,674

18 Claims.

My invention relates to an extensible antenna, and especially to an extensible antenna of the type employed for automobile radio sets where an extensible section of the antenna is telescopically mounted within the tubular section thereof.

One phase of my invention is addressed to the problems of means for shifting the extensible section of the antenna where the shifting is to be accomplished not by a direct manual push or pull on the extensible section, but by means of a fluid permitting a more or less remote control or operation of the shifting.

One of these problems is that of supplying a sufficient shifting force to overcome those resistances and other difliculties which might be expected at various times throughout the life of the antenna. The normal resistance to shifting of the extensible section-will be rather substantial. The piston head or piston cup employed on the extensible section in a fluid shifting produces friction. Likewise, the bearings or journals for the extensible member produce friction if they are to have a sufficiently snug fit to prevent rattle. In addition, even with so relatively corrosion-resistant a material as stainless steel, a continued exposure of the extensible section will result in accumulation of road films, dirt deposits, and occasionally ice, all of which will con siderably add to the resistance to shifting.

As my solution to this problem of adequate fluid shifting force, I prefer to make the driving fluid a hydraulic one, to employ positive pressure for the shifting, and to employ that positive hydraulic pressure for shifting the extensible section both ways; that is, for both the extension and the retraction. As contrasted with suction which has heretofore been used in shifting an extensible antenna section, my positive pressure, being freed from the inherent pressure limitations of suction, may practicably involve rather high pressure with the result that the effective piston area may be kept quite small, which reduces the required over-all diameter of the antenna, and in turn makes possible a more sightly and graceful appearance, economy in cost, and a minimizing of obstruction to vision. Another advantage of the positive pressure is that an unusually high pressure can be built up when and if there is excessive sticking or resistance to the shifting, and it can be built up enough to overcome that sticking or resistance, even though normally the shifting is accomplished by a much lower positive pressure.

The hydraulic pressure, employing a non-compressibl'e medium, has the advantage that where a piston or diaphragm type, for example, of actuating or master compressor is used to effect the shifting, the position of the piston or diaphragm may be taken as an indication of the extent or completion of the shifting movement of the extensible section; and this is true whether the master compressor be power actuated or manually actuated. This is of considerable advantage in designing mechanism for automatically terminating the stroke of a piston or diaphragm of a power-operated compressor. It is also a great help to the operator especially where the antenna is mounted in such a position that he cannot readily observe the degree of extension. This advantage also becomes important where it may be desired to extend the antenna only partially, as for instance where full extension is not required for good reception and a full extension might cause danger of contact with overhead obstructions such as low branches of trees along country roads.

The employment of a positive fluid pressureand especially a positive hydraulic pressure-for shifting the extensible section both ways, extension and retraction, perfects the positiveness of the shifting. It eliminates the uncertainty of reliance in whole or in part upon the weight of the extensible section to effect retraction. Where the diameter of the antenna is held to a minimum, as is a feature of my invention, the diameter, and consequently the weight, of the extensible section becomes insufficient reliably to overcome the frictions and resistances which may have to be overcome to effect retraction. This feature makes it practicable to mount the extensible antenna in positions where one cannot conveniently reach the extensible section manually to retract it in the event of excessive sticking. Extensible antennae raised by fluid pressure have heretofore been confined to positions on the automobile such as a bumper mounting or an exterior mounting at one side of the cowl, for example, where one would experience no difliculty in reaching the extended section to push it down in the event of excessive. sticking. But these locations have no been so favorable for radio reception, because the extended section would still lie largely along side the body of the automobile and largely within the overall height thereof, rather than being extended to a position quite above, and free from proximity to, the steel car body and from its objectionable signal reducing effect.

A more detailed structural feature of my invention in connection with the two-way positive hydraulic pressure shifting is the utilization of the hydraulic conduit to the far end of the cylinder section of the antenna as a structural truss to reinforce the rather small-diametered cylinder section. I thus avoid the expense and added obstruction to vision of providing separate structural reinforcement. This reinforcement which I provide protects the cylinder section of the antenna against too readily becoming permanently bent. Such bending strains might result from accidental encounter with something. Or they might result from the leverage effect of the extended section being flexed or whipped about by air resistance at high speed.

Another phase of my invention is concerned with a master compressor for effecting extention and retardation of an antenna under positive hydraulic pressure, a power drive for the master compressor, a control for the power drive, and also a manual operator for the master compressor, and the placement and mounting thereof.

Still another phase of my invention is the lo cation and mounting of my extensible antenna. My preferred locationand a location which is made uniquely practicable by my two-way positive hydraulic shiftingis along, and more or less parallely spaced from, the Windshield on the outside thereof. Where, as is now the usual design, the windshield comprises right and left panels or panes forming a medial ridge, the cylinder or fixed section of my antenna is mounted to extend along, but slightly spaced outwardly from, the trim strip of the ridge and, if desired, continue upwardly therebeyond to approximate the height of the crown of the top, with the extensible section, when extended, protruding.

This location has many advantages. It lies directly ahead of, and so close to, the trim strip along the ridge of the V windshield that it does not objectionably add to obstruction of vision. Even when retracted, the antenna is outside of the car body, which makes it more effective than if it were located within the body when retracted. When extended, the extension lies quite above the top of the car and quite free from objectionable proximity thereto, whereby the extension is most effective for signal reception.

This location brings the lower end of the antenna, which terminates substantially at the cowl at the base of the windshield, into very close proximity to the radio set which is generally and most desirably mounted at the mid point of the instrument board immediately below and behind the ridge of the windshield. Thus, the length of the lead-in from the antenna to the set is reduced to a minimum. It does not needlessly and objectionably add to the capacity of the antenna in a region where it would be of no useful effect and where, in fact, being exposed to the influence of the numerous ignition and other circuit wires leading to the switches on the instrument board, a long or circuitous lead-in would otherwise pick up motor and miscellaneous noise static.

Another advantage of this location with the antenna wholly substantially above the cowl and forwardly of the windshield is that the cowl, hood, instrument board and adjoining portions of the windshield frame, all being of sheet metal, act quite effectively as shields to protect the antenna from the miscellaneous electrical influences of ignition and other circuits of the motor, lights, direction signal interrupters, and the like, parts of which circuits run to the instrument board beneath the cowl and hood.

Another feature of my invention in this connection is that, even though the connections to the antenna whereby the extensible section is shifted must most conveniently and feasibly extend down below the cowl and behind the instrument board within the electrical influence of the previously mentioned miscellaneous circuits, and subject to the electrical effect of the ignition spark, I am able to avoid those shifting connections to the antenna having any electrical effect upon the antenna, by the very simple expedient of employing non-metallic rubber and fabric hoses and a non-conducting liquid therein. Thus, it becomes a matter of no moment, as regards disturbing signal reception by the antenna, how much metal may be employed in the master compressor or the mechanism for operating or controlling it, nor where those metal parts are placed as regards electrical fields, because the antenna is insulated from them by the non-conducting hose and liquid.

In the interests of economy and convenience, I prefer to mount the master compressor and its operating mechanism rather near the base of the antennafor practical convenience perhaps mounting them in whole or in part upon the receiving set. But it is an advantage of my invention that if another location should be desired, there is no complication on account of the operating connections between the antenna and the master compressor being rather long and extending considerable distances through what would otherwise be objectionable electrical influences.

Further advantages of my preferred location of the antenna along the ridge of the V windshield and extending upwardly from the cowl is that it better conforms itself in appearance to the lines of the car, permits a desirable rearward inclination both for appearance and yielding against overhead obstructions, and better protection against the likelihood of being accidentally damaged because of its being placed where garage mechanics, service station attendants, and others are less likely to come in contact with it. Yet, by my invention I have been able to place the antenna in this preferred and desirable location without objectonable consequences on account of its being shifted by intermediate means.

While I consider the above-discussed location of my extensible antenna to be preferable in most instances, I contemplate that my two-way hydraulically operated extensible antenna may be installed in other locations, such as within the central mullion of the windshield, or behind the mullion and within the passenger compartment, or, especially, at one side of the cowl where the stationary cylinder section is below the cowl and between the side wall and lining of the automobile, with the extensible section rising above the cowl.

My invention is also concerned with the provision for mounting the extensible antenna and especially to provision whereby the antenna, master compressor, and connections therebetween may be preassembled at the factory and installed in the automobile without the necessity of breaking the seal of the hydraulic system, with the attendant difficulties of refilling and bleeding the system.

The foregoing, together with further objects, features and advantages of my invention, are set forth in the following description of specific embodiments thereof, as illustrated in the accompanying drawings, wherein:

Fig. 1 is a medial vertical section through the windshield, cowl and instrument board of an automobile, showing an installation of my antenna and. operating mechanism therefor in its preferred. location, the extensible sectionpf'the antenna being retracted Fig. 2 is a longitudinal section through. the. antenna and its mounting, upon an enlarged! scale;

Fig. 3 is a transverse section taken on the line 1 Fig. 4 is a detail plan-section of the antenna mountingv taken on the line 44 of Fig. 2;:

Fig. 5 is a. diagrammatic front elevation ofa portion of the face panel of the radio set exposed through the instrument board showing. the motor 1 switch for controlling the. shifting of' the shiftable section of the antenna;

Fig. 6 is a longitudinal section through a motor-- ing of my extensible antenna and its operating mechanism and Fig. 9 is a vertical transverse section of. the antennaof Fig. 8 and the associated parts of the body, the antenna being of a. modified, threesection design.

As exemplary of the: preferred. location and mounting of my extensible antenna, 1 have i1 lustrated in Figs; 1 and 3 portions. off the body of an automobile including a cowl I with the usual ventilator therein, an instrument board I2, a windshield I3, and a top H. The windshield is set into the usual marginal. rubber chan} nel l dressed by a marginal trim strip Hi. The juxtaposed near edges of thediverging' planes of the two windshield panes, as shown in Fig. 3, are mounted. inthe respective channels of an H- shaped rubber double'channel |;'l dressed by' an outer trim strip |8 along theyridge for-med between the diverging panes.

The radio receiving set l9, which may be of conventional design, is installed beneath and for:- wardly of the instrument board with the. panel face 2-llof the set protruding through, or'mounte d in front of, an opening inthe instrument board, as shown. The radio receiving set It is, as shown, housed and electrically shielded bythe usual sheet metal box.

The automobile and receiving set, as thusfar de cribed, are of a usual and standard construe;-

tion. My extensible antenna comprises a cylinder section 2| and an extensible section 22 telescopically mounted therein and protruding from In the form shown in the upper end thereof. Figs. 1, 2 and 3, the cylinder section 21 is fixed and the extensible section is a rod which, cidentally, constitutes a piston. The extensible section, at its lower and inner end, carries a pis+ ton head 23, which may be formed by a pair of oppositely facing piston cups clamped by a tee;-

minal nut against a stop sleeve 24 fixed on the section 22. The upper or outer end of the extensible section 22 carries a ball tip 25 which limits its retraction. which is formed from tube stock, and like the rod of the extensible section is preferably of stainless steel, is closed at its upper end byfa plug 26 brazed or otherwise secured thereon and provided with a peripheral bead 26" contacting the end of the tube. A terminal fitting threaded on to the outer reduced end of the The cylinder section T plug 26 and, together with. the. end of the plug,

comprises a string. packing gland 28 to supplement the rather close fit of the extensible section with the. bores of. the plug, and terminal. fitting to seal against loss of the liquid medium under pressure;

The'lower end of the tube of the cylinder section 2| is brazed into the headed upper. end of a mounting tube 29, which extends vertically down through the cowl I0 and by means of a lower nut 29 serves to clamp together the lower andupper insulating mounting members 30 and 3|. The lower end of the mounting tube 29 is connected by a hose 32 to communicate with the chamber on one side of the diaphragm of the master compressor 33 of Figs. 1 and 6. In this way liquid medium displaced by the master compressor may press against the-bottom of the piston. head. 23.

To supply the liquidmedium from the other side of the diaphragm. of the compressor tothe top side of. the piston. 23, I provide a collateral conduit tube 34.turned laterally at its upperend to communicate with the bore of the cylinder section 2| througha hole therein just below the plugZS. The lower end of the'collateral tube 34 is collared or shouldered at. 35 horizontally opposite the head of the mounting tube 29, and also extends down through the mounting members 30 and 3| to aid, by means of a nut 36, in clamping thetwo mounting members together. The lower end of the collateral tube 34 is connected by a hose 31 to communicate with the master compressor 33 on the other side of. its diaphragm.

Because the windshield is inclined rearwardly and the antenna is likewise inclined rearwardly, the two tubes 23 and 34 are bent, as indicated, just above the mounting members.

In. order that the antenna may be preassembled with the compressor and hoses at the factory, without the necessity of breaking the seal of the liquid. system and refilling it for installation, the mounting of the antenna is sov arranged that the antenna is inserted. from beneath the instrument board and cowl upwardly through the cowl opening 3.8 provided for the purpose.

The hole 38 in the cowl is made a little larger than the over-all dimensions of the assembled cylinder section 2| and collateral tube 34, and therefore the portion of the lower mounting member 30, which protrudesthrough the opening 38, is correspondingly contoured. The contour is, in general, oblong. The central opening of the upper mounting member is likewise oblong in shape. so that the upper member 3| may be slipped down over the antenna after it is protruded upwardly through the, cowl. C-washers 39 and 40 are then inserted between the. lower side of the head of. the mounting tube 29 and collar 35, respectively, and the upper faces of the upper member 3| and core of the lower member 30, whereupon the nuts 28 and 36 are tightened to clamp the two portions of the members. and the intervening, rubber washer 4| together about the margins of the cowl opening 38. This securely mounts the lower endxof the antenna in. the cowl between the windshield. and the ventilator and centrally of the windshield. v

The antenna. is further fixed in its rea'rwardl'y slanting medial position by a clamp 42. The clamp 42 is in the form of a metal strap bent peripherally to embrace a split insulating block 43. The mating faces of the halves of the block are conformed to receive the cylinder section 2| and the collateral tube 34, as shown in Fig. 3. The divergent rearward ends of the clamp 42 are terminally turned inwardly to engage the lateral edges of the ridge trim strip N3 of the windshield, being clamped by a screw M. The clamp 32 is positioned near the top of the windshield the better to support the cylinder section 2! toward its upper end. The clamp 42 also serves to maintain the antenna parallel with the ridge of the Windshield, at a spaced distance therefrom, and in visual alignment with the ridge strip l8 and donble channel I I, whereby to minimize interference with the vision of occupants of the front seat.

Although anchored by the clamp 42, the cylinder section 2| of the antenna would be subject to some flexure, especially if the cylinder section were made from relatively light tube stock. Such fiexure might result from accidental impact or from the resistance of the extended section 22, which is apt to whip at high speeds or in high winds due to air resistance. Such flexure might break the brazed connection of the forwardly turned upper end of the collateral tube 34. To help the collateral tube 34 in its function of trussing and reinforcing the cylinder section 2! against flexure, I braze short spacing struts 45 of tube stock between the cylinder section 2i and the collateral tube 34 at intervals therealong.

The compressor 33, shown in Figs. 1 and 6, is of the diaphragm type. It comprises peripherally flanged upper and lower cups ii: and ll clamped together with a diaphragm separator 48 therebetween. An operating shaft 19 for shifting the diaphragm is, for the purpose of a motor drive, preferably formed as a screw 50 journaled within the compressor and having liquid-tight threaded connection with a nut i fixed and sealed to the central region of the diaphragm 48. A small reversible electric motor 52 is drivingly connected with the shaft 49, whereby axially to shift and flex the diaphragm 48 in either direction. The compressor 33 and motor 52 may conveniently be mounted by brackets 53 and 54 on the rear of the casing of the receiving set i9, if the latter is mounted near the center of the instrument board. The reversible motor 52 is controlled by a threeposition switch 55 which, for convenience, may be carried on the exposed front panel of the receiving set, as shown in Figs. 1 and 5. The manually engageable lever of the switch 55 may be normally spring urged to its 013? position, being raised to cause the motor to rotate in one direction which will raise or extend the extensible section of the antenna and depressed to a down position which will cause the motor to operate in the opposite direction to retract or lower the extensi ble section.

A slip clutch 55 is operatively interposed between the compressor shaft 49 and the armature of the motor, and so adjusted as to slip when the maximum intended pressure is built up in the system or when the diaphragm 48 ha shifted to the extreme position allowed by the compressor.

The compressor 33, the hoses 32 and 37, the cylinder section 2 l, and the collateral tube 34 are all filled with a hydraulic medium. This is preferably a liquid which combines the characteristics of not readily leaking past the packings and piston head, maintaining a fairly constant fluidity within the wide temperature ranges in which the automobile is to operate, constituting a fairly good lubricant, non-deteriorating of the metal, rubber, and such parts which come in contact with itand electrical non-conductivity, whereby it will not in effect become part of the antenna despite the fact that it extendsbelow the cowl and forwardly of the instrument board away-e44 where it is subject to so man objectionable electrical influences. A mixture of forty percent by volume of castor oil and sixty percent of diacetone alcohol is satisfactory for my purpose.

The hoses 32 and 31 are likewise preferably formed wholly of rubber and fabric so that, like the liquid, they will not extend the reception of the antenna down below the cowl. The lead-in 51 may be electricall connected by the clamping nut 29 or 36 to th base of the antenna. As shown in Fig. 1, this lead-in traverses only a minimum distance beneath the cowl, thus subjecting the antenna to only a minimum of motor noises and other stray noises; and even this can be further minimized by a shielding jacket for the lead-in.

The operation of my extensible antenna device, as illustrated in Figs. 1 to 6, inclusive, is as follows:

When the antenna is in its normal retracted position as shown, it extends but a short distance beyond the top of the windshield but still preferably withinthe level of the crown of the top, where it will not be engaged by any obstruction which'the automobile body will clear. When the antenna is to be extended, the finger lever of the switch 55 is raised to its up position. This closes a circuit of. the motor 52 to rotate the compressor shaft 49 in a direction which will flex the diaphragm 48 downwardly. Downward flexure of the diaphragm 48 displaces the liquid medium from the lower cup 41 through the hose 32 and into the bottom of the cylinder section 2|, where it presses against the cylinder head 23 and extends the section 22. At the same time the upwardly moving piston head 23 displaces the liquid medium from the upper part of the cylinder section 2! and down through the collateral tube '34 and the hose 3'! to the interior of the upper cup 45, where it occupies the enlarging volume above the diaphragm 48. When and if there is any undue resistance or sticking of the extensible member, an abnormall high pressure may be built up, within the limits of the power of the motor and the setting of the slip clutch 56, sufficient to overcome the abnormal ticking or resistance, whereupon the extension will continue under a more normal and more moderate hydraulicpressure. When the extensible section 22 has reached the limit of its upward travel, the excessive hydraulic pressure which will then be built up on the lower side of the diaphragm, or the resistance encountered by the diaphragm reaching its limit of movement, will cause the clutch 56 to slip. When the operator hears the clutch slipping, and-therefore knows that the antenna has been full extended, he releases the switch button 55 which then returns to its normal off position. Because the nut 5| of the diaphragm i locked against the screw 5!] of the shaft 49, the piston will be held in its resulting downwardly flexed position until the motor is operated to turn the shaft in the opposite direction. Therefore, the extensible section is locked in its up position by the confined column of liquid below the piston head 23, which will maintain'the compressor extended despite its weight and any vibration of the antenna. The stop sleeve 2 3 on the extensible section 22 adjoining the. piston head 23 serves as an abutment against thelower end of the plug 26 to limit the piston head passing into the region of the bore Of the cylinder section 2i, where the upper end of the collateral tube 34 communicates with it. This relieves; wear on the cups of the piston head 23 and avoids the piston going beyond the point where hydraulic pressure from the collateral tube 34 will be efiective against the top side of the piston head.-

When the antenna is to be retracted, the procedure is reversed. The switch lever 55 is pushed to its down position, closing a motor circuit which causes the motor to turn in the opposite direction and raises the diaphragm 48. (In Fig. 6 the diaphragm is shown in its intermediate position, but it will be understood that in practice it will normally rest in an up position or a down position, depending upon whether the antenna is retracted or extended.) The hydraulic medium expelled by raising the diaphragm 48 is conducted through the hose 31 and collateral tube 34 to the upper end of the cylinder section 2 l, where it presses down on the piston head 23, shifting the extensible section 22 back to its retracted position. At the same time, hydraulic medium expelled from the lower end of the cylinder section 2| by the depending piston head 23 flows back through the hose 32 to the lower side of the diaphragm occupying the increasing volume on the lower side thereof. When the operator hears the clutch 56 slipping, he releases the lever of the switch 55, which returns the switch to off position and results in the extensible section being hydraulically locked in its retracted position. i

By permitting the switch 55 to return to its ofi position before the extensible section has reached the limit of its up or down movement, the antenna maybe hydraulically locked at some desired intermediate degree of extension.

In Figp'? I have shown a manually operable compressor, and the compressor is of the piston type rather than of the diaphragm type, although I contemplate that a piston type may be used with the motor operation or the diaphragm type with hand operation.

The compressor 53 comprises a cylinder '59 pivoted at 60 on to a bracket supported on the back of the housing of the receiving set IS, a two-way piston 6 l working in the cylinder 59, and a hand lever '62 pivoted at 63 to the protruding end of the piston rod 64. The hand lever is pivotally mounted at B to a bracket also carried at the back of the set casing. The hoses 32 and-'31 communicate with the cylinder 59 at its respective ends. A finger-controlled detent 66 working in notches of a' quadrant 61 may be employed to effect a hydraulic lock of the extensible section in its fully extended position, its fully retracted position, or in some desired intermediate positions. The position of the piston iii of the master compressor, and consequently the position of the hand lever 62, may be taken as an indication of the position of the extensible section of the an tenna.

In the installation of Fig. 7, as in the installation of Fig. l, the parts which effect the shifting of the extensible antenna need not interfere with the transversely moving horizontal link 68 for operating the windshield wipers.

Referring back to Fig. 2, it will be seen that when the extensible section 22 is shifted upwardly, the volume of liquid displaced from above the piston head 23 is a little less than the increase of volume of the cylinder section2l below the rising piston head on account of the volume of rod-like body of the extensible section 22. This slight difference is accommodated by the flexible hoses 32 and 3?. Where the compressor is actuated by Ia sliding rod which extends inwardly from one side of the compressor as in the modification of .Fig. 7, the rodfill passes through the chamber of the compressor .59 which is connected to the upper end of the cylinder section .2 I. It will readily be understood that as the rod 64 is moving into the compressor 59 the extensible section 22 is moving out of the cylinder section 2i, and vice versa. Consequently, the decrease of volume due to entry of the rod 64 into the compressor 59 tends to compensate for the increase of volume due to the outward movement of the extensiblesection 22.

In Figs. 8 and 9 I have illustrated another location and mounting for my extensible antenna, and the motor-operated compressor therefor. .In Figs. 8 and 9 I have also shown a modified .form of extensible antenna where the hydraulically extended section is itself tubular and carries a third and rod-like section telescoped therein.

Here the cylinder section H1 .is mounted at its upper end by insulating mounting members Tl about the margins of an opening in the left-hand end of the cowl just forward of the corner post of the body. The major portion of the cylinder section It lies below the cowl and between the side panel i2 and the lining T3 of the 'b'ody, be ing supported at its lower end by a bracket 14. From the lower end of the cylinder section 101a hose [5 leads to thecompressor 16. The compressor-l6 and its motor 11 may conveniently be mounted along with the cylinder section It in the space between the side panel 12 and the linin 13.

Another hose [8 leads from communication with the interior of the cylinder section 10 near its upper end and just below the mounting members H and down to the other side of the compressor 16. The extensible section 79 of the antenna of Figs. 8 and 9 is a double section, comprising-a tubular section'80 telescopically mounted within the cylinder section 10 and a rod section 8| which, in turn, is telescopically mounted within the tubular section 80. The tubular section 80 carries apiston head 82 at its lower end working within the bore of the cylindersection ID. The tubular section 80 is slidably journaled in the upper end of the cylinder section HI and sealed thereto by a plug 83, terminal fitting 84, and packing 85, similar to the plug 26, fitting 21 and packing 28 of Fig. 2. The rod section 8| has a simple mechanical telescopic, mounting within the bore of the tubular section 85] and is manually extended and retracted in reference thereto, the rod section carrying a ball tip 86 for this purpose.

The hydraulic shifting and locking of the tubular section 8i] between its retracted position and extended position or desired intermediate position is accomplished in the same manner as explained in connection with Figs. .1 to 6. During this hydraulic shifting, the rod section 3| will preserve its position in reference to the hydraulically shifted tubular section Bil.

Thus, the rod seotion8l maybe fully telescoped into the tubular section .80, in which event the hydraulic extension, when effected, will give the antenna about twice its. fully collapsed length. Or, the rod section Bil may be pulled out to its full extension in reference to the tubular section 80, in which event the hydraulic extension of the tubularsection will increase the length of the antenna from twice to three times-its fully retracted length. In the latter extended position,

the first length of the antenna will come up to the level of the cowl, the second to the level of the top of the body, and the third to a considerable distance above the top.

While I have thus described and illustrated these specific embodiments of my invention, I contemplate that many changes and substitutions may be made therein without departing from the scope or spirit of my invention.

I claim:

1. An extensible antenna comprising mutually telescoping antenna sections, and means for extending and retracting the antenna, comprising a piston on one of the sections, a hydraulic compressor having a shiftable divider, compressor actuating means, force multiplying means operatively connecting the actuating means to the divider, and conduit means communicating a hydraulic medium from one side of the divider to one side of the piston head and from the other side of the divider to the other side of the piston head, whereby shifting the divider in one direction will move a predetermined quantity of liquid from the compressor on one side of the divider and simultaneously will move a similar quantity of liquid into the compressor on the other side of the divider to extend the antenna under positive hydraulic pressure, and back-shifting the divider will retract the extensible section under positive hydraulic pressure.

2. An extensible antenna comprising a cylinder section, an extensible section shiftably telescoped therein and protruding from an end thereof, and means for extending and retracting the extensible section including a piston head at the inner end of the extensible section, and a substantially rigid tube collateral to the cylinder section for communicating fluid under pressure from one end of the collateral tube to the bore of the cylinder section near the end thereof from which the extensible section protrudes, whereby to supply fluid under pressure behind the piston head to force the retraction of the extensible section, the collateral tube being fixed to the cylinder section at a plurality of longitudinally spaced points along their lengths whereby to truss and reinforce the cylinder section against; bending.

3. An extensible antenna and means for mounting the antenna along the front side of a windshield of an automobile and above its cowl, comprising a cylinder section, an extensible section telescopically mounted in the cylinder section to extend from its upper end, a piston head carried on the inner end of the extensible section and working in the bore of the cylinder section, mounting means at the base of the cylinder section adapted to pass through an opening in the cowl adjoining the bottom of the windshield for insulatedly mounting the base of the cylinder section, an insulated clamping member adapted to engage a trim strip of the windshield near the top of the windshield insulatedly to 'fix the cylinder section toward its upper end, and 'electrically non-conductive conduit means adapted to be connected to a fluid compressor and leading" to the mounting means for supplying fluid under pressure through the mounting means to the bore of the cylinder section on both the upper and lower sides of the piston head for extending and retracting the extensible member.

4. The combination of an automobile body having a windshield, a cowl at the base of the windshield and an instrument board depending from the cowl, an extensible antenna comprising a cylinder section and an extensible section slidably telescoped therein and in electrical contact therewith, means for insulatedly mounting the antenna in an upwardly extending position along the windshield at the forward side thereof with the base of the antenna at the cowl, a compressor mounted below the cowl, electrically nonconducting hose means communicating between the compressor and the cylinder section to supply an electrically non-conducting fluid medium from the compressor to the cylinder section for extending and retracting the extensible section, the cowl constituting an electrical shield to shield the antenna from electric influence of circuits beneath the cowl, and an electrical conductor connected with said cylinder section through said mounting means for connecting the antenna to a radio receiving set.

5. The combination of an extensible antenna comprising a cylinder section and an extensible section mounted pistonwise therein, a two-way compressor, and hoses connecting the two sides of the compressor with the cylinder section above and below, respectively, the piston head of the extensible section, a hydraulic medium filling the cylinder section, compressor and hoses whereby actuation of the compressor will extend and retract the extensible section under positive hydraulic pressure, means for mounting the antenna and compressor on an automobile with the antenna in insulated relation above, and the compressor below, its cowl, the hoses and hydraulic medium being non-conductive of electricity between the antenna and the compressor.

6. The combination with an automobile of a cowl at the base of its windshield, a small hole in the cowl, a fluid-operated extensible antenna comprising a cylinder section and an extensible piston section working therein, mounting means for insulatedly mounting the base of the antenna on the cowl at said hole with the antenna extending upwardly therefrom, a master compressor mounted below the cowl, and a pair of conduits extending from the compressor through the region beneath the cowl and through the cowl hole and mounting means to communicate with the cylinder section near the lower and upper ends thereof to supply a fluid from the compressor to both sides of the piston section for extending and retracting the antenna, the conduits and fluid being non-conductive of electricity from the region below the cowl to the antenna.

7. The combination according to claim 6, wherein the cowl hole is of sufficient area and shape to pass the extensible antenna whereby the antenna may be installed and removed by inserting it upwardly through the cowl hole, or withdrawing it downwardly through the hole, as the case may be, without breaking the fluid seal of the conduits to the antenna and compressor.

8. An extensible antenna comprising a length of tubing constituting a cylinder section, an extensible section slidably mounted in the cylinder section to protrude therefrom. a piston head on the extensible section working in the bore of the cylinder section, a closure for the far end of the cylinder section having a bore for slidably journaling the extensible section, another length of tubing fixed to, and disposed alongside, in rein-- forcing relation to, the cylinder section and at its far end communicating with the interior of the cylinder section, the near ends of the cylinder section and collateral tube being adapted to receive fluid under pressure to Work against the near and far sides of the piston head for extending and retracting the extensible section.

9. The combination with an extensible antenna having a cylinder section and a piston-headed extensible section slidably mounted pistonwise therein, of two sealed hydraulic systems one operating upon one side of the piston head and the other operating upon the other side thereof, and means for jointly and simultaneously displacing oppositely the hydraulic medium in the two systems to shift the extensible section and for hydraulically locking the extensible member in a plurality of shifted positions within the range of its movement.

10. The combination of an extensible antenna comprising a cylinder section and a pistonheaded section working therein and extensible therefrom, a compressor having a shiftable divider, conduits communicating between the compressor at the two sides of the divider and the cylinder section at the two sides of the piston head, respectively, a hydraulic medium filling the compressor, conduits, and cylinder section, a motor, and force multiplying power transmission means between the motor and compressor divider for shifting the divider to displace the medium through the conduits and between the cylinder section and compressor for hydraulically extending and retracting the extensible section.

11. The combination according to claim 10, wherein the power transmission means includes a slip clutch which slips under hydraulic pressure resistance to shifting of the divider when the extensible member reaches the limit of its movement.

12. The combination according to claim 10, wherein the power transmission means includes a screw shaft rotated by the motor and passing through the divider, and a nut carried in the divider and having threaded engagement with the screw shaft. I

13. The combination of an antenna comprising a cylinder section and a piston-headed extensible section slidably mounted therein and protruding from one end thereof, a master compressor having a shiftable divider, an operating rod connected to the divider and slidably protruding through one end of the compressor, a conduit communicating between the cylinder section at the end thereof from which the extensible member protrudes and the compressor at the side of the divider from which the rod protrudes, and another conduit communicating between the cylinder section at the other end thereof and the compressor at the other side of the divider, and a hydraulic medium filling the compressor, conduits, and cylinder section for extending and retracting the extensible section as the divider is shifted, the decrease of volume due to entry of the rod into the compressor tending to compensate for the increase of volume due to projection of the extensible section.

14. An extensible antenna comprising a. cylinder section and an extensible section mounted pistonwise therein, means mounting the upper end of the cylinder section in a hole in the cowl of an automobile at a lateral end thereof, with the cylinder section lying beneath the cowl and between the side wall and lining of the automobile, and a hydraulic compressor, also mounted beneath the cowl and between the side wall and lining, and communicating with the cylinder section near its upper and lower ends for extending and retracting the extensible section under positive hydraulic pressure, the cylinder section, compressor and communications therebetween constituting a liquid-filled system.

15. An extensible antenna device comprising a tubular antenna section, a second antenna section in relatively slidable mutually telescoping relation to the one section, and means for relatively extending and retracting the sections comprising a piston for the second section working within the tubular section, a liquid compressor, and liquid conduit means communicating between the compressor and the tubular antenna section on the respective sides of the piston and forming a return line to the compressor for liquid displaced by the piston on its movement in either direction, the tubular antenna section, the conduit means and the compressor forming a liquid filled closed hydraulic system partitioned into two closed hydraulic sub-systems by the piston and the compressor adapted for incremental movement of said piston longitudinally of said tubular section, by relative displacement of liquid by the compressor, and corresponding extension or retraction of the second section, and for holding the second section in any selected extended or retracted position determined by the quiescent condition of the compressor.

16. An extensible antenna device for an automobile according to claim 15 wherein said antenna sections are mounted substantially wholly to extend upwardly from the cowl of the automobile, the compressor is mounted below the cowl, the conduit means are, at least in part,

electrically non-conducting whereby not substantially to extend the antenna system below the cowl, and the liquid in the hydraulic system is electrically non-conducting.

17. An extensible antenna comprising a cylinder section, an extensible section slidably mounted in the cylinder section, and means for extending and retracting the extensible section comprising a piston head thereon working in the bore of the cylinder section, a hydraulic compressor having a shiftable divider, compressoractuating means, force multiplying means operatively connecting the actuating means to the divider, and conduit means communicating a hydraulic medium from one side of the divider to the cylinder sectio at one side of the piston head and from the other side of the divider to the cylinder section at the other side of the piston head, the arrangement of the compressor and conduit means being such that shifting the divider in one direction will extend the extensible section under positive hydraulic pressure on one side of the piston head and effect corresponding relief by withdrawal of hydraulic medium on the opposite side of the piston head, and shifting the divider in the other direction will retract the extensible section under positive hydraulic pressure on said opposite side of the piston head and effect corresponding relief of hydraulic pressure by withdrawal of hydraulic medium from said one side of the piston head.

18. The combination with an antenna of means for mounting it on an automobile having a rearwardly slanting windshield and a cowl extending forwardly from the base of the windshield, means connecting the antenna toward its upper end adjacent to the top of the windshield, means for securing the base of the antenna insulatedly at a hole in the cowl adjacent the base of the windshield, and a pair of conduits leading through the cowl hole and the base mounting means for supplying fluid under pressure to extend and retract the antenna.

OTTO E. WAGENKNECHT.

CERTIFI CATE 0F CORRECTI ON Patent No. 2,5u5, 91 1;. March it, 191m.

' OTTO E. WAGENKNECHT.

It is hereby certified that errorappears in the printed specificationof the above numbered patent requiring correction as follows: Page i, first column, line 11.1, for "pressure." read -pressures-; and second column, line d6, for "no" read --not; page 2, first column, 'line 16, for "retardati on read retraeti on-; line 55, after "protruding" insert --there above; and that the said Letters Patent should be read with this correction therein that the same may conform to the reeord of the case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 191m.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFI GATE OF CORRECTI 0N.

Patent No. 2,514.5, 9141;. March 1h, 19%.

OTTO E. WAGENKNECHT.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring eorrection as follows: Page 1, first column, line 141, for "pressure." read "pressures-1, and second column, line k6, for "no" read -not--; page 2, first column, line 16', for "retardation" read retraeti on--; line 55', after "protruding" insert thereabove--; and that the said Letters Patent should be read with this correction therein that the same may conform to the reeord of the case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

